In my U.S. Pat. No. 2,990,653, an application of rocket technology is employed to increase particle velocity in sandblast cleaning application by the use of internal burners powered by compressed air and a hydrocarbon fuel. The use of pure oxygen as the oxidant in a fuel and oxygen mixture fed to the combustion chamber of the internal burner has the severe advantage of melting some types of abrasives during particle transit through the gun, conventionally introduced upstream and of the internal burner combustion chamber. For this reason, pure oxygen could not be used as the oxidant source.
More recently, I have found that by using extremely high combustion pressures and introducing abrasive particles in the expanded gas, which has a temperature significantly below that of the products of combustion exiting from the combustion chamber, such allows the practical use of oxy-fuel internal burners for blast cleaning applications. This led to later work in similar air-fuel devices, in which the abrasive was added just upstream of the restricting nozzle passage, thereby eliminating the transit of the particles through the combustion chamber as exemplified by my U.S. Pat. No. 4,540,121.